What, exactly, is the effect that you are looking for? A “God-beam” or “God-ray?” This topic has been discussed here before …
Also: one way to considerably-simplify your task is to composite this effect, “on top of” the otherwise-finished scene that you have right now. You literally create a new scene, correctly aligned, which consists only of “the rays.” Then, you use the compositor to superimpose it, to whatever degree of “opacity” looks good to you, and in whatever “shade of color.” The audience will never know. (Or care.)
Now, you can address these two very-different concerns separately. Blender’s “node-based” compositor offers you absolute control over exactly how the two images are to be combined.